Preparation of cellulose acylnitrate



Patented Nov. 7, 1933 PREPARATION OF CELLULOSE ACYL- NITRATE Cyril J. Stand and James T. Fuess, Rochester,

N. Y., assignors to Eastman Kodak Company, 7 Rochester, N. Y., a corporation of New York No Drawing. Application December 31, 1930 Serial No. 505,966

Claims.

Our invention relates to the making of cellulose acyl-nitrate by partially de-esterifying cellulose nitrate and then acylating the de-esterified nitrate.

An object of our invention is to make possible a process which allows the nitrogen content of the cellulose acyl-nitrate to be easily controlled so that a uniform product is produced in every carrying out of the process. As a change in the content of acyl or nitrogen may alter the physical properties of the cellulose derivative to a considerable extent, it becomes important that the composition of the cellulose acyl-nitrate from successive processes be uniform.

Previously cellulose aceto-nitrate for use in the making of photographic film, rayon, lacquer, etc., has been prepared by the nitration of cellulose acetate, by the acetylation of cellulose nitrate, or by the use of m xtures which embody both these principles. Previously by the second method mentioned it has been attempted to nitrate the cellulose to some desired point and then acetylate. However, the diificulty of obtaining a certain nitrogen content on each successive nitration is apparent. Also as this reaction is carried out, some of the nitrate radicles are substituted by acetyl radicles so that the original nitrogen content is no determinant of the composition of the resulting product. Although it may be possible by proper control to obtain a fairly uniform product, this control is difficult in contrast to the control made possible by the present invention.

Another object of our invention is to provide a process of making a cellulose nitro-acetate from de-esterified cellulose nitrate which results in a product which has a lower viscosity and better solubility, for instance in acetone, than the cellulose nitro-acetate which is produced by acetylating cellulose nitrate which has not been de-esterifled to a reduced nitrogen content as has previously been the practice. Obviously this is a decided contribution to the cellulose derivative art.

By our invention a product is formed which is soluble in acetone as it is when it comes from the acylation bath which eliminates the necessity of hydrolyzing. As is well known, the usual practice to procure acetone-solubility of an acetate or nitro-acetate of cellulose is to hydrolyze subsequent to the step of acylation.

We have found that a material, which is very satisfactory for any of the common applications of a cellulose acyl-nitrate, is obtained if cellulose nitrate is de-esterified by some means, e. g., by a de-esteriiying agent, all of which are well known in the prior art, and then acylated by any of the methods commonly employed. The de-esterification is carried out to the desired point, depending on the amount of nitrogen desired in the resulting product.

As an illustrative example of the operation of our invention, we give the following. It is to be understood that this is only one embodiment of the invention: Cellulose nitrate containing about -14% of nitrogen is placed in an approximate 34% aqueous solution of ammonium hydrosulfide, and the mixture is allowed to stand at room temperature (-25 C.) until the nitrogen content is 6% or more (as desired by the operator). It is to be noted thatthe nitrogen content of the final product may be regulated by merely controlling the time that the de-esterification mixture is allowed to stand. .The material is then washed until neutral and air dried. About 100 grams of the dried material is placed in a mixture of about 700 grams of glacial acetic acid and about 4 c. c. of mixed catalyst (1 sulphuric acidz3 phosphoric acid) and the mixture is allowed to stand for 2-6 hours at 35-40" C. The mixture is then cooled to about room temperature. About 300 grams of acetic anhydride preferred) is added and the mixture is worked until a dope is formed. The temperature may then be slowly raised to about 40 C. and the dope may be precipitated in water.

Any other acylation reaction known in the art compatible with the conditions of operation of this invention may be used instead of the one givenin the example, .as desired, such as the use of acyl chlorides or of a fatty acid and an impelling agent, these reactions being well-known in the art. Also, although the acetyl compound is preferred, any of the other fatty acid groups both saturated and unsaturated may be substituted for the acetyl and may be attached to the de-esterified cellulose nitrate in the same manner as is ordinarily used to attach the same group to cellulose. For example, butyryl may be attached to the deesterified cellulose nitrate by means of an ester- What we claim and desire to secure by Letters Patent of the United States is:

1. The process of making a cellulose acyl-nitrate which comprises the acylation of a cellulose nitrate which has been partially de-esterified whereby there are less than 3 nitrate groups to every 'Cs cellulose unit.

2. The process of making a cellulose acyl-nitrate which comprises partially de-esterifying a cellulose nitrate whereby there are less than 3'nitrate groups to every Cs cellulose unit and acylating the resulting product.

3. The process of making a cellulose aceto-nie trate which comprises partially de-este'rifying a cellulose nitrate whereby there are less than 3 nitrate groups to every Cs cellulose unit and acetylating the resulting product.

4. The process of making a cellulose butyro-nitrate which comprises partially de-esterifying a cellulose nitrate whereby there are less than 3 nitrate groups to every Cs cellulose unit and butyrating the resulting product.

5. The process of making a cellulose aceto-nitrate which comprises acetylation of a cellulose nitrate which has been partially de-esterified whereby there are less than 3 nitrate groups to every Cs cellulose unit.

CYRIL J. STAUD. JAMES T. FUESS. 

